THE Opposition today confirmed it would add 15 per cent to the tax on superannuation paid by 3.6 million low wage earners if it wins government, but hinted at a replacement scheme for battlers.

Debate over the fate of the tax relief highlighted that superannuation policy will be a central issue at the September 14 election.

Shadow treasurer Joe Hockey said a Coalition government would not make unexpected changes to superannuation which would harm people's savings, and said Labor's policy would be a feature of the election campaign.

But the Government counted today by accusing the Coalition of taking money from the retirement savings of most workers earning $37,000 and lower a year, including 2.1 million women.

The extra tax for largely unskilled workers would come from the Coalition abolishing the $1 billion a year Low Income Superannuation Contribution scheme which has operated since July.

"Categorically, once and for all, the Coalition needs to bite the bullet,'' said Minister for Superannuation Bill Shorten today.

Mr Shorten called the Opposition policy the "Sheriff of Nottingham tax".

"Mr Abbott wants to give the richest mining companies in the world a tax cut, and he wants to put it on 3.6 million working Australians,'' he said.

Opposition spokesman on superannuation, Mathian Corman, today told news.com.au the Coalition had been consistent in opposing the tax offset because the Government wanted to fund it from the Mining Resources Rental Tax - usually known simply as the mining tax.

The MRRT has yet to raise any revenue because of a fall in mineral prices, but the Government has funded the scheme from consolidated revenue. The Opposition has opposed all programs to be funded by the MRRT, except the plan to increase compulsory superannuation contributions from nine per cent to 12 per cent.

"Importantly, while we will not support any of the other promises Labor has recklessly attached to the so far non-existent and always unpredictable mining tax revenue, we will however release our own policies on how we intend to encourage increased retirement savings across all income brackets as we approach the next election,'' said Senator Corman.

The Government measures the Coalition would drop because they are set to be funded by the mining tax are: pension increases; tax cuts; increases to family benefits; a $6500 instant asset write-off for small businesses.

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